Lymphocytotoxic antibodies in family members of patients with multiple sclerosis.

Cold-reactive lymphocytotoxic antibodies were found in sera from 14 of 21 (67%) patients with multiple sclerosis. A significantly (p less than 0.01) greater frequency of these antibodies was also demonstrated in patients' household members (12 of 18 [67%]) compared to siblings living elsewhere (3 of 14 [21%]) or normal controls (1 of 13 [8%]). No difference in antibody frequency was found between consanguineous and non-consanguineous family members. These findings suggest that the increase frequency of lymphocytotoxic antibodies in these multiple-sclerosis patients and their family members is an indicator of the presence of a transmissible agent, probably a virus, in many patients with multiple sclerosis.